Wiznet makers

In this article, we are going to explore the w5500 module with our rp2040 boards. w5500 is a quite powerful device that allows a wired connection.

We will also try to give a solution to a tedious problem: the device does not provide an SSL connection, and in a trusted world like this, It’s another big limit, fortunately, OPEnS developed a wrapper that contains in one packet all BearSSL implementation, and this, with a quiet amount of resources, allows standard Arduino Ethernet to use secure connections.

Devices

The W5500 chip is a Hardwired TCP/IP embedded Ethernet controller that provides an easier Internet connection to embedded systems. W5500 enables users to have Internet connectivity in their applications just by using the single chip in which TCP/IP stack, 10/100 Ethernet MAC, and PHY are embedded.

WIZnet‘s Hardwired TCP/IP supporting TCP, UDP, IPv4, ICMP, ARP, IGMP, and PPPoE protocols. W5500 embeds the 32Kbyte internal memory buffer for the Ethernet packet processing. If you use W5500, you can implement the Ethernet application by adding a simple socket program. It’s a faster and easier way rather than using any other Embedded Ethernet solution. Users can use eight independent hardware sockets simultaneously.

SPI (Serial Peripheral Interface) is provided for easy integration with the external MCU. The W5500’s SPI supports 80 MHz speed and a new efficient SPI protocol for high-speed network communication. To reduce the system’s power consumption, W5500 provides WOL (Wake on LAN) and power-down mode.

Features

• Supports Hardwired TCP/IP Protocols: TCP, UDP, ICMP, IPv4, ARP, IGMP, PPPoE
• Supports 8 independent sockets simultaneously
• Supports Power-down mode
• Supports Wake on LAN over UDP
• Supports High-Speed Serial Peripheral Interface(SPI MODE 0, 3)
• Internal 32Kbytes Memory for TX/RX Buffers
• 10BaseT/100BaseTX Ethernet PHY embedded
• Supports Auto-Negotiation (Full and half-duplex, 10 and 100-based )
• Not supports IP Fragmentation
• 3.3V operation with 5V I/O signal tolerance
• LED outputs (Full/Half duplex, Link, Speed, Active)
• 48 Pin LQFP Lead-Free Package (7x7mm, 0.5mm pitch)

There is a wide series of w5500 devices, but the most popular are 2 in particular.

The less expensive one is the w5500 that you can see in the photo.

But now there is a compact version named w5500 lite, very interesting as a device for production.

Here my selection of tested ethernet devices w5500 lite - w5500 - enc26j60 mini - enc26j60

Wiring

Here my selection of rp2040 boards Official Pi Pico - Official Pi Pico W - Waveshare rp2040-zero - WeAct Studio rp2040

This device uses an SPI interface; by default, I will use a base SPI interface.

Raspberry Pi Pico

Waveshare rp2040-zero

Remember that the wiring for this device is based on a tutorial that you can find here.

Library

A wide selection of libraries exists, but the standard one Is the best choice. You can find It in the standard Arduino library manager.

SSLClient

This library and device do not support SSL, so to add these features exists an alternate library named SSLClient that needs a little patch of Ethernet.

SSLClient adds TLS 1.2 functionality to any network library implementing the Arduino Client interface, including the Arduino EthernetClient and WiFiClient classes. SSLClient was created to integrate TLS seamlessly with the Arduino infrastructure using BearSSL as an underlying TLS engine. Unlike ArduinoBearSSL, SSLClient is entirely self-contained and does not require any additional hardware (other than a network connection). _(cit.)

SSLClient with Ethernet

If you are using the Arduino Ethernet library, you will need to modify the library to support the large buffer sizes required by SSL (detailed in resources). You can either modify the library yourself or use this fork of the Ethernet library with the modification. To use the fork: download a zipped copy of the fork through GitHub, use the “add a .zip library” button in Arduino to install the library, and replace #include "Ethernet.h" it with #include "EthernetLarge.h" in your sketch. Alternatively, if, for some reason, this solution does not work, you can apply the modification manually using the instructions below.

Buffer extension

I also notice that you probably must change something to get good stability.

In SSLClient.h you must change this line.

to

Manual Modification

First, find the location of the library in the directory where Arduino is installed (C:\Program Files (x86)\Arduino on Windows). Inside this directory, navigate to libraries\Ethernet\src (C:\Program Files (x86)\Arduino\libraries\Ethernet\src on Windows). Modify Ethernet.h to replace these lines:

With this:

You may need to use sudo or administrator permissions to make this modification. We change MAX_SOCK_NUM and ETHERNET_LARGE_BUFFERS so the Ethernet hardware can allocate a larger space for SSLClient. However, a downside of this modification is that we can only have two sockets concurrently. As most microprocessors barely have enough memory for one SSL connection, this limitation will rarely be encountered in practice.

Code

Now we try to do a simple WebRequest with a native client.

But first, we write the code needed for the connection, we try to ask the IP to the DHCP server, and if It fails, we start a connection with a static IP.

Initialize device

Ethernet uses the default SPI interface default, so first, we must set the correct SS pin (probably not needed).

You must specify a MAC address also.

Then we try to make a DHCP request.

But If it fails, we try to make a static IP connection with these parameters

and here is the connection code

Simple HTTP request

First of all, we’ll try to make a simple HTTP request. I chose an online service created to test this kind of request.

I’m going to use a simple service given from httpbin.org, and you can use the same REST API in HTTP and HTTPS.

Remember that HTTP work on port 80 and HTTPS on 443, so you must validate a certificate to query the endpoint on the 443 port.

To make our connection, we use the basic EthernetClient.

And then, we try to connect and ask for a GET endpoint.

In the loop, wait for a response from the server.

And then read the response and send it to the serial.

And finally, the complete sketch.

The result is this.

HTTPS request

Now, if we change the endpoint to port 443, the request will be to a secure server with SSL encryption.

And we obtain this response.

So the problem is that request and response messages aren’t transmitted using SSL (Secure Sockets Layer) or its successor TLS (Transport Layer Security). To add this feature, we are going to use SSLClient.

Retrieve certificate

To use an SSL connection, we need the server certificate, but in this case, SSLClient uses a trick given by BearSSL implementation. A minimal x509 verification engine that allows using of Trust Anchors.

I add a simple online generator that you can find here.

You must only write the site’s address (httpbin.org) in the first input box, click Generate code, copy the code, and put it inside a file called trust_anchors.h and put it inside the sketch folder.

Here is the content of trust_anchors.h.

Add SSLClient wrapper

Code

Now we are going to add the SSLClient library and the trust_anchors.h file.

I also changed the Ethernet library with EthernetLarge instead of the change described in the upper section.

Then apply the wrapper EthernetClient with all the references of Trust Anchors. The file contains generated trust anchor array names TAs with length. TAs_NUM.

And we change the port to 443 (HTTPS).

Here is the complete sketch.

Now when we execute the sketch, we obtain this output.

Thanks

I use this SSLClient library in my EMailSender library to use Gmail SMTP server (SSL) with Ethernet. Unfortunately, SSL connections need a lot of resources, but Arduino SAMD, STM32, rp2040, and ESP32 have them.